1. Field of the Invention
The present invention relates to a method and an apparatus for transmitting voice information representing language through the core network of a mobile radio network, between connected core networks of mobile radio networks, and from mobile radio networks to wire-bound users of a PSTN.
2. Description of the Prior Art
As it is known from different manual textbooks such as Jacek Biala, 1994, ISBN-3-528-15302-4, Vieweg Verlag, mobile radio communication occurs between two mobile stations in a mobile radio network from a mobile station (User Equipment UE) via an air interface (Air Interface/Radiolink) to a base station (or, respectively, a Radio Network Controller RNC) via switching centers (Mobile Switching Centers MSCs or Media Gateways MGW) and via a further base station to a second mobile station (UE). Since a number of users normally telephone in a mobile radio network, considerable amounts of data are transmitted via the core network of a mobile radio network; particularly, between switching centers (media gateways).
It is proposed in WO93/00778A1 to transmit voice data in the core network of a mobile radio network in a compressed format and not in a 64 kb/s-FCM format. As a compressed format, WO93/00778A1 suggests the voice data compression format used between mobile stations and base stations/radionet controller (e.g., according to UMTS) for optimally utilizing the extremely limited channel capacities on an air interface; voice data therefore being transmitted in the format (for example, according to UMTS standard) in which they are transmitted via an air interface also within the core network of the mobile radio network. For this purpose, known (under UMTS, etc.) transcoders (which, in a base station or MSC etc., previously have converted voice data from the compressed air interface format into a non-compressed 64 kb/s-PCM format for the transmission in the core network of a mobile radio network) are switched off or, respectively, are bypassed (Transcoder-Free-Operation=TrfO=Uncoded Operation.
However, it is difficult to implement this transmission method since the transmission of voice data in a mobile radio network in the TrfO data format in the core network does not allow many features such as mixing voice data of a number of callers given a conference call or importing tones or announcements into transmitted voice data.
An object of the present invention, therefore, is to enable an optimized use of transmission resources, when bits of voice information are transmitted in a mobile radio network, by avoiding the above disadvantages.